A preventive single-sided knee brace for athletes includes independently pivotable and laterally rigid upper and lower leg bars interconnected at laterally rigid polycentric clevis joints of a shield plate assembly. Straps affixed to a knee plate of the shield plate assembly encircle the leg adjacent the knee joint and buckle to the knee plate to hold the assembly adjacent the lateral side of the knee joint in any position of leg flexion. The upper leg bar extends from the shield plate assembly along the outside of the upper leg and is secured to the leg at the bar's upper end. Similarly, the lower leg bar extends from the polycentric joint along the outside of the lower leg and is secured to the leg at the bar's lower end. The upper and lower leg bars are shaped to follow the contour of the leg and bridge the knee joint to hold the shield plate assembly laterally spaced from the side of the knee joint.
